A baby who wakes hot and sweaty at night often has more to do with fabric and layering than anything else. Tight weaves and synthetic blends trap heat and moisture against the skin, so sweat has nowhere to go. Muslin cotton is woven loose and open on purpose, which lets air move through the fabric and lets moisture evaporate instead of sitting there all night. Muslin pyjamas built for hot, humid nights are worth looking at here, because the open weave does the work that a thicker or synthetic fabric can't.
Layering matters as much as the fabric itself. One light muslin layer, or Epic's double-layer muslin pyjamas, is usually plenty when the room is warm, and a cotton sheet does more good than a blanket pulled up to the chin. If you're unsure how much to put on, this guide to layering a baby in hot weather walks through it room by room. Keeping the room itself cool and letting air circulate helps too, since no pyjama fabric can fully compensate for a stuffy room.
Washing matters too. A cold wash on a gentle cycle keeps the weave soft without breaking it down, and tumble drying muslin on low, or just hanging it to dry, keeps it ready for the next hot night. Skip fabric softener and high heat: both coat or stiffen the weave and work against the airflow that keeps a baby cool. Epic's muslin pieces run from newborn through age four, ship worldwide with tracked delivery, and unworn returns are accepted within 30 days if a size doesn't work out.