What's your routine for fasting? I've been doing 16:8 intermittent fasting for a couple years now (but that slipped really bad along with everything else these last couple months) and it really helps maintain and lose weight for me. I usually break fast at noon and wrap up the eating between 6 and 8 in the evening.
I love running in the morning while fasting, I don't crash and I feel energized afterwards. I'm sure running properly fueled would make the runs a little easier/faster but I like the effects running while fasting has on my metabolism and energy.
I try to mix it up to prevent the body getting too accustomed to the fast. When I break the fast I exercise as much as I can that day.
Normal routine is one meal every 24 hours. That meal is in the evening nowadays but I'd like to get back to morning meals because I think it's far better overall. I don't really consider my one-a-day meal a fast anymore because my body got used to it. Pushing my meal to the following morning (~36 hours) or to a two-day fast is also pretty normal and easy for me at this point.
Once you get used to two day fasts, you can easily do a full week or longer. Those initial 48 hours are the worst. Avoid carbs/sugar before and after fasting if you want easy-mode. Seriously, most of the cravings associated with fasting come from your brain wanting carbs.
I drink tea and water during the fast. The calories from milk, juice, pop, etc still count. Plain coffee should be okay but I'm not a coffee drinker. Sometimes I mix in some raw cacao (sunscreen) and/or dried mushroom powder. That's about 50 calories so technically I'm breaking my fast, but the body burns through it rather quickly and I never noticed it making a difference.
I also do deep-breathing exercises and cold training (showers, ice baths, polar plunge, etc) to improve the body's oxygen capacity (I'm sure there's a more official term). Fasting is nice but the body quickly becomes accustomed to it if you don't have other stressors pushing you.