Sikhs are not any kind of Muslim.
Here is a short review of Middle Eastern and South Asian religions:
Before historical times there were only Hindus in India and pagans everywhere else. Most of the inhabitants of India remain Hindus, and are polytheists with dozens of major gods and some 70 million minor deities.
The Jews arose in Babylonia about 2000-1500 BC before their adventures in Egypt and the Holy Land. The Zoroastrians developed at about the same time in Persia. These were the first two great monotheistic religions, and may have arisen from a common root. The Jews of course persist in Israel and the West, while the Zoroastrians are now almost wiped out by the Muslims.
Separately, Gautama Buddha lived in India in ca. 300 BC and founded the school of knowledge that bears his name, and is as much a philosophy as a religion. Very few Buddhists remain in India, but there are large numbers of devotees in Tibet, Thailand, and East Asia.
Christianity of course arose in the first century AD. There are numerous Christians in India, some converted by missionaries in modern times, while others belong to Christian traditions dating back to the first few centuries AD, some of them supposedly even evangelized by St. Thomas himself. However, they are far fewer than Hndus and the other main religions.
Islam dates to the 7th century in Arabia and the Middle East. Shi'ite Muslims followed the son-in-law of Mohammed and are now found primarily in Iraq and Iran. Sunni Muslims are the majority elsewhere, including Pakistan and India, and followed other leaders after the split with the Shi'ites in the century after Mohammed's death. Sunni Islam moved eastward and conquered the Indian subcontinent in the 1000-1500 AD time frame (the Rajput, Delhi and Moghul Empires.)
The Sikhs appeared in Punjab in the late 1400's. This is a new religion and is not Hindu or Muslim, although it incorporates elements of both older religions. It is monotheistic and highly egalitarian, and in many respects is the most admirable of all the Eastern religions. The Sikhs were persecuted by the Muslim Moghul Empire and developed a mighty warrior tradition in their defense. These are the people one typically sees wearing the turban, and it is a great slander and mistake to attack them for being Muslim.
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Hinduism is not exactly polytheistic, because the term ‘Hinduism’ itself is an arbitrarily constructed concept.
The Bhagavad-Gita, the main scripture of what we know today as Hinduism, is deeply monotheistic, and echoes that declaration throughout its length.