In spite of the lack of any formal organisation, how was the BKU able to sustain itself and the protest started in 1988 in Meerut?

Through clan networks.

Another novel aspect of these mobilisations was the use of caste linkages of farmers. Most of the BKU members belonged to a single community. The organisation used traditional caste panchayats of these communities in bringing them together over economic issues. In spite of lack of any formal organisation, the BKU could sustain itself for a long time because it was based on clan networks among its members. Funds, resources and activities of BKU were mobilised through these networks.