Many different answers to this question. First, let's look at why "drain the tank" is useful. You're trying to improve your peak performance and if you train at 70%, you'll not be as effective at training your performance at 100%. Now this needs to be power output, not just riding until you drop, but you want to be doing hard workouts on a programmed schedule -- not every day, but on a rotation with other workouts (see below) -- because they will train your body to adapt at the limit of its current performance. And that is what training is really about -- extending your limits.
What to be careful of? First, let's say you do a 100% effort and achieve a personal best. Let's say you even rest til your heart is back down and you've had a chance to recover your phosphate levels in your blood. Then the next one you can only do at 85% of that. Well, you aren't training to extend your limits any longer, and that second effort is just tearing you down (because your next effort will likely only be at 75%) and still isn't training you at your limit. It always comes back to the unpleasant, painful fact that the best training is what extends your limits, and to do that you have to train at your limits.
Your body will actually respond quite quickly with improvements if you can train at the limit. Many people who train endlessly and don't find improvement are often training at 80% and just never teaching their body to work at new levels. The Australian national track coaches have always had a policy with their athletes -- you get out on the track and you go for max. If you set a personal best, you stop and go home. No more efforts. Both physiologically and psychologically, it's the strongest approach to take. Additionally, if you get out on the track and you do well under your previous level, you also go home. Whatever the reason is, you aren't going to be training in a productive manner that day and anything you do will be counterproductive.
These are of course approaches focused on power efforts and to some extent on anaerobic efforts. When it comes to aerobic efficiency or to anaerobic tolerance, you can ride at, say, 85% and train your body to extended and tolerable output at higher levels. For a time trialist that kind of training can support your ability to ride at a higher level for an extended period of time (and bear in mind that your body may be capable of considerably more, but your mind can only handle so much pain, so this is psychological training as much as physiological for all but the most incredibly gifted). Efforts like Tabatas are one way to push this kind of training, but note that you have to do them at 85%, not 100%. After a series of 85% repeat intervals, you will still be tanked, but if you do your first at 100%, then your next is at 85%, your next at 75%, etc., you aren't doing them right. Your body is rather dumb and adapts for exactly what it is experiencing, and that last workout isn't training it for continuous high-level output.
You said hill climbs. If you want the power and want to be able to work at the limit of your tolerance in respiratory and muscle pain, workouts like Tabatas may not be as useful. Instead, you may want to do power curves, where you start at 80% and ramp yourself up to 100% until you completely die. Your body should be able to subsist for quite a while at 80%, but here you're taking yourself right to the limit and riding until you are completely spent. Then stop, fall onto a crash pad, throw up, and when you're feeling better, take a bath and a nap and rest. No more workouts. The trick on that effort is to make the ramp at the right slope -- too fast and you kill yourself pretty fast, too slow and you're going to tire your muscles so that your 100% effort isn't at the same high mark. Just be sure if you are watching power that you keep increasing until you quit. Lots of loud music really helps. Indoors, a strong fan helps. And seriously, get a crash pad for bouldering and spread it next to your bike. When you finish, you can just fall over onto it, curl up, and die. You don't want to try to sit on your bike after this effort. Spinning your legs down sounds nice in practice but if you've really done 100%, your legs won't turn any longer. This is what you see when a rider pulls his absolutely max to a major hilltop finish and then just freezes up on the bike and has to be caught by a soigneur before he crashes and carried by two team staffers to his bus. Unfortunately, most people train hill climbs at a sustaining level and become pretty fit, but don't actually adapt their bodies to climb faster. If you do a workout like this (and it's really only one workout in a day -- good for those of us who have to work and lead a life as well as train) once a week, you should see a progression in power. If your progression dips, you need to rest. You want each new effort to be at least some margin better than the previous one. Same rule as for the Aussie track riders -- if you do better, you stop, go home, and rest. If you can't get close to your previous level, your body needs rest or you are otherwise distracted or handicapped, so stop, go home, and rest.
Everyone has different ideas about how to train, of course. But this is an easily quantifiable approach. It doesn't take a lot of time and can be done very nicely on a trainer indoors. In particular it's tailor-made for something like a Wahoo Kickr or at least a resistance trainer plus a power meter. And it works well for self-coaching because you have simple goals and don't need extensive physiological testing. Like every other recommendation on training, iyou have to find what works for you. I've just found that with riders trying to do what you say you are seeking, this approach addresses both physiological and psychological limits (especially the latter, since that's usually the one most of us run into first) and increases your performance. And that's worth all of $0.02.