Wiktionary
builder's tea
n. (context UK English) black tea, brewed strong and served in a large mug with milk and sugar.
Wikipedia
Builder's tea
Builder's tea is a British English colloquial term for a strong cup of tea. It takes its name from the inexpensive tea commonly drunk by labourers taking a break. A builder's tea is typically brewed in a mug with a teabag (as opposed to loose tealeaves in a teapot), usually with full-fat milk and at least two teaspoons of sugar.
Usage examples of "builder's tea".
She inclined her head in acknowledgement, and refused a cup of Mrs Grundy's industrial-strength builder's tea.