For a thicker cold foam, try using heavy cream or a combination of milk and cream. Experiment with different flavored syrups to create your own signature cold foam variations. Lavender, caramel, or hazelnut would all be delicious! If you don't have a milk frother, you can use a French press or even a whisk to create cold foam, although it may require more effort and time. Chilling your glass mugs beforehand will help keep your cold brew and cold foam at the perfect temperature.