People with lupus are known to react badly to legumes which are beans, peas and lentils. Alfalfa sprouts are in this group too and that's why they are not allowed. Other foods may or may not cause problems, it depends on the individual. But everyone with lupus needs to be careful with legumes and limit or avoid them to prevent flare-ups.
Everything that's unhealthy in general is also unhealthy for people with lupus. Processed foods with lots of preservatives are problematic, as well as foods high in sugar and salt.
Moderate consumption of everything else is okay. Variety is key. It's important to eat foods that have real nutritional value with vitamins, minerals, carbohydrates and protein. I personally try to eat organic and all natural. I cook my meals and try to include a little bit of everything in my diet.