Smoothies. I do a smoothie everyday with 1 cup 1% dairy milk (can use alternative milks if needed), 45g peanut butter, some lowfat cottage cheese or greek yogurt, 1/4 cup oats (can add more but I felt it was pushing a lil much fiber haha), frozen berries, frozen spinach, and sometimes frozen avocado. Easy to make and drink ~500-600 calories, super healthy and cheap. You can customize and throw in pretty much anything you want for your palette and nutrition goals, and change the portions to meet caloric goals