Legumes, legumes and more legumes. You shouldn't need excessive amounts of sugar unless you're working out to exhaustion regularly, and it certainly won't make you bulkier; you need protein primarily for that. Be thankful you don't have a sweet tooth. It plays havoc with your gut and hormones. If you're looking for dense calories, my tip is lots of beans, seeds, nuts, peas, quinoa and lentils. They all have a great mix of carbs, protein, fibre and micronutrients. Lots of chilli's, pastas, porridge, stirfrys and stews. For fruits, look towards more sour fruits - berries, cherries and grapefruit. If you still struggle after that, try a vegan mass gainer powder (no lactose). Everyday, drink one minimum. That's about 30g of protein and 40g of carbs, 400kcal, in about 500ml worth of volume. Initially you'll probably struggle with stomach volume. Eat until you feel near to bursting, do that as much as you can, and that will stop being a problem within a week or two. I went from 63kg at 6'3" (due to 3 months in a hospital bed with a busted spine, and no appetite from the opiates) to just shy of 95kg within a year, only working out 2 times a week doing the same 5 exercise - deadlifts, squats, bench-press, bent-over rows and overhead press. Any questions feel free to ask!